Research Of Varibale Temperature Measurement Technique For Complex Permittivity Of Dielectric Materials By Short-circuited Line Method

Microwave materials are widely used in aerospace, military, medical and other fields. In many microwave systems, the performance parameters of materials directly impact the performance of equipment, particularly complex permittivity. Therefore, it has a great significance to accurate knowledge of value and variation of complex permittivity for proper operation of the equipment. Generally speaking, most of equipments only need to complete the work under normal temperature. Therefore, grasping the variation of complex permittivity in room temperature environments is enough. But, when the operating temperature is at several hundred degrees or even more, it is very hard to choose the right material to produce equipment. At the same time, complex permittivity of the dielectric material changes non-linear, and will have an enormous impact on the device. Therefore, establishing a variable temperature dielectric property of materials testing system to test different variations of microwave dielectric properties at different temperatures accurately and provide reference data for the production of microwave equipment has great significance.Based on the traditional theory of short-circuited line method and past experience in test engineering, we used rectangular waveguide as the basic transmission line, made high temperature waveguide and cooling waveguide, and added high performance directional coupler, coaxial-rectangular waveguide mode converter, cooling device to testing structure. Then, build a set of variable temperature dielectric property testing system around the testing structure with other subsystems, and used automated testing software to finish the variable temperature testing on the dielectric material near 15 GHz. In addition, we analyzed the influence on testing waveguide and the sample from high temperature environment, and completed model updating of the gap and deformed waveguide. The technical indicators are as follows:Test frequency:Ku Band (dot frequency)Test temperature:Room temperature to 1200℃Test range:Room temperature:εr’=1.0～12 tan δε= 0.001～0.11200℃:εr’=1.0-12 tanδε=0.005～0.1Test errors:Room temperature:|Δεr’/εr’|≤5% |Δtanδε/tanδε|≤14% tan δε+0.001 1200℃:|Δεr’/εr’|≤10% |Δtan δε/tanδε|≤28% tan δε+0.002...